Recently, attention has been given to organic EL (electroluminescence) devices, as devices for use as next-generation light emitting displays with low consumption power. An organic EL device basically has a pair of electrodes and at least one organic layer that includes a light emitting layer made of an organic light emitting material. Such an organic EL device is self-luminous and can emit multicolor light derived from the organic light emitting material. Therefore, attention has been focused thereon for use as displays for television (TV), etc.
The organic EL device is configured by sandwiching at least one organic layer including a light emitting layer between two electrode layers having opposite electrodes to each other (sandwich structure), in which each organic layer is composed of an organic film of several nm to several tens of nm. The organic layer sandwiched by the electrode layers is supported on a substrate, and the organic EL device is formed by sequentially stacking an anode layer, the organic layer, and a cathode layer on the substrate in this order. In the case where a plurality of organic layers are present, the respective organic layers are sequentially stacked over the anode layer.
In methods for manufacturing such an organic EL device, vacuum evaporation and coating are commonly known as a technique for forming a film of each organic layer over the anode layer formed on the substrate. Among these, vacuum evaporation is mainly used, because of the capability of increasing the purity of the material for forming the organic layer (organic layer-forming material) and the ease of achieving long life span.
In the above-mentioned vacuum evaporation, the organic layer is formed by performing vapor deposition using an evaporation source provided at a position facing the substrate in a vacuum chamber of a deposition apparatus. Therefore, the evaporation source is provided corresponding to the organic layer. Specifically, the organic layer-forming material is heated by a heating unit provided in the evaporation source so as to be vaporized, and the vaporized organic layer-forming material (vaporized material) is discharged through a nozzle provided in the above-mentioned evaporation source so as to be deposited over the anode layer formed on the substrate. Thus, the organic layer-forming material is vapor-deposited over the anode layer.
In such vacuum evaporation, a so-called batch process or roll process is employed. The batch process is a process in which the organic layer is vapor-deposited over the anode layer per one substrate on which the anode layer has been formed. Meanwhile, the roll process is a process in which: a strip-shaped substrate which has been wound up in roll form with the anode layer formed thereon is unwound continuously (in a so-called roll-to-roll manner); the respective organic layers are continuously vapor-deposited over the anode layer while the unwound substrate is supported on the surface of a can roll that is being rotationally driven and is moved together with the rotation of the can roll; and the substrate over which the organic layers have been vapor-deposited is wound up into a roll. Among these, it is desirable to employ the roll process for manufacturing organic EL devices, from the viewpoint of reducing the cost.
However, in the case where the roll process is employed in vacuum evaporation, the emission color varies from a desired emission color (unevenness occurs), as a result of which organic EL devices of low quality may be manufactured in some cases.
On the other hand, there is proposed a technique of decreasing the distance between the evaporation source and the substrate in vacuum evaporation, in order to reduce the amount of water to be introduced into the light emitting layer from the viewpoint of extending the life span (see Patent Literature 1). However, when the distance between the evaporation source and the substrate is decreased as mentioned above, the deposition amount of the organic layer-forming material decreases from the center to both ends of the substrate in the width direction of the substrate, as a result of which the film thickness is rendered larger at the center than at both ends. Therefore, organic EL devices of low quality with the emission color varying from the desired emission color are more likely to be manufactured, particularly, in the width direction of the substrate.
Therefore, in order to reduce the difference in deposition amount of the organic layer-forming material between the center and both ends in the width direction of the substrate in the roll process, it is proposed that the substrate is divided into at least two regions in its width direction by flow regulating members parallel to the direction in which the substrate is moving, and the organic layer-forming material is discharged through a slit defined by the flow regulating members, so as to be deposited over the substrate (see Patent Literature 2).